On a cloudy 27 degree day, Dr. Tertius Venter biked past the brown Swannanoa River east of Asheville, N.C. The 60-year-old plastic surgeon from South Africa wore a black helmet, custom biking shoes, and a green cycling shirt. He carried one cell phone strapped to his bike handle and in a backpack carried necessities for the trail: battery packs, headphones, and toilet paper. 1120 km behind him, 6880 km to go.

He has no sponsors, no grand plans, just a burning vision and two good friends with a rented van. Venter left New York City on June 3. He planned to cross the continent over the next two months, ending his trip on the Golden Gate Bridge in San Francisco. Now more than a month into his trip, Venter is cycling across Texas in the sweltering July heat. Along the way, he tells audiences at churches and hospitals, “One in three people in the world have no access to medical care. … People really are in desperate need, and we can do something about it.”

That message so gripped Venter that he gave up his private practice in 2006 and endures long separations from his wife so he can operate unpaid in impoverished places across the world. He works with volunteer organizations including Mercy Ships and Operation Smile.

Venter first heard about Mercy Ships more than 15 years ago, when a ship docked near his clinic in East London, South Africa. He toured the ship and three months later volunteered for the first time. He has been with Mercy Ships every year since then.

Venter returned to his practice and family, no longer interested in material success, wanting to become a full-time volunteer. For his wife Trudi, the decision didn’t seem so simple. She explained her thinking in a documentary (The Dawn of a New Day) that Venter gave WORLD: “It was a very big shock. … My feelings of rejection were very intense.”

In 2006, Venter closed his practice and Trudi gave her reluctant assent. Since then, Venter sees his family less than three months a year. Trudi hated seeing the ship because it meant Venter would be leaving: “I miss that protection … just being together.” Her friends advised divorce, but Trudi refused to give up on the marriage: “I know that I can trust him. … This is a time for me to rely on God and not on Tertius for my identity.”

The two talk every night and email back and forth. The next time he will be with his wife is mid-October: “People ask me, ‘Why are you doing this?’ I don’t know, I have to.” When not volunteering, Venter can’t stay idle. Starting last year he began biking thousands of miles, telling stories about patients and the billions without care: “You think you hear about all these infectious diseases that kill so many people and don’t realize lack of basic surgery kills more.”

As he cycled, Venter described a farmer from Madagascar with a growth covering most of his back. The man could barely walk. Every day he lived in pain. Venter said if the farmer had access to a local doctor, he could have had the growth removed years ago. He spent two hours treating the man: “A relatively simple operation; but if you can’t go anywhere, those things can keep on growing.”

He told of a 60-year-old with “a tumor on his jaw that has been growing for 17 years.” The man heard about Mercy Ships and walked with his son for more than two days to reach the ship. A surgeon told the man his tumor was so big he could die from an operation. The man said, “Well, it doesn’t matter; I’m already dead.”

Venter relishes “reaching out to people and telling them they are a human being, and we care for you.” Venter performs more than 100 operations on each Operation Smile trip: “A lip we can repair in 45 minutes and give them a normal look. Someone needs to do that.”

As the sun set, Venter stopped pedaling. His friends’ van pulled up beside him. It was almost 10 p.m., and he barely managed to crawl into the backseat. After a late start that morning, Venter struggled to reach his daily 100-mile goal. He fell asleep immediately. Tomorrow he would be up early to start all over again.